switch to "protoc-gen-grpc-python-prebuilt" for the grpc-python-plugin

docs/notes/2.32.x.md

@@ -53,6 +53,10 @@ Pants will attempt to only preserve the `mypy` cache when `mypy` returns a [prob
 
 The default version of mypy used by Pants has been updated to [1.19.1](https://mypy-lang.blogspot.com/2025/11/mypy-119-released.html).  This includes support for the new "Fixed‑Format" cache.
 
+The `grpc-python-plugin` tool now uses an updated `v1.73.1` plugin built from  <https://github.com/nhurden/protoc-gen-grpc-python-prebuilt]. This also brings `macos_arm64` support.
+
+
+
 #### Shell
 
 #### Javascript

src/python/pants/backend/codegen/protobuf/python/grpc_python_plugin.py

@@ -1,27 +1,37 @@
 # Copyright 2020 Pants project contributors (see CONTRIBUTORS.md).
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
-from pants.core.util_rules.external_tool import TemplatedExternalTool
+from pants.core.util_rules.external_tool import ExternalTool
+from pants.engine.platform import Platform
 
 
-class GrpcPythonPlugin(TemplatedExternalTool):
+class GrpcPythonPlugin(ExternalTool):
     options_scope = "grpc-python-plugin"
     help = "The gRPC Protobuf plugin for Python."
 
-    default_version = "1.32.0"
+    # https://github.com/nhurden/protoc-gen-grpc-python-prebuilt maintains a
+    # composite versioning strategy with both the grpc plugin version and the
+    # version of "protoc-gen-grpc-python-prebuilt" that built it
+    default_version = "v0.3.1+v1.73.1"
     default_known_versions = [
-        "1.32.0|linux_arm64 |9365e728c603d64735963074340994245d324712344f63557ef3630864dd9f52|5233664",
-        "1.32.0|linux_x86_64|1af99df9bf733c17a75cbe379f3f9d9ff1627d8a8035ea057c3c78575afe1687|4965728",
-        "1.32.0|macos_arm64 |b2db586656463841aa2fd4aab34fb6bd3ef887b522d80e4f2f292146c357f533|6215304",
-        "1.32.0|macos_x86_64|b2db586656463841aa2fd4aab34fb6bd3ef887b522d80e4f2f292146c357f533|6215304",
+        "v0.3.1+v1.73.1|linux_arm64 |aa7730e447a829f61ed0da9b9c0974d56fba8984806ac4a4d984da0c998f1a3d|14536184",
+        "v0.3.1+v1.73.1|linux_x86_64|17952bf233ed86841c15a454a378cc4ef78f2610313c3159d3e58f987ba5f656|13874656",
+        "v0.3.1+v1.73.1|macos_arm64 |7cb578b187eb959402cf3434699dffda0f46c4380baa5648e1e75fc9440d3d12|32170440",
+        "v0.3.1+v1.73.1|macos_x86_64|7cb578b187eb959402cf3434699dffda0f46c4380baa5648e1e75fc9440d3d12|32170440",
+        # Old versions from binaries.pantsbuild.org
+        "1.32.0|macos_arm64 |b2db586656463841aa2fd4aab34fb6bd3ef887b522d80e4f2f292146c357f533|6215304|https://binaries.pantsbuild.org/bin/grpc_python_plugin/1.32.0/macos/x86_64/grpc_python_plugin",
+        "1.32.0|macos_x86_64|b2db586656463841aa2fd4aab34fb6bd3ef887b522d80e4f2f292146c357f533|6215304|https://binaries.pantsbuild.org/bin/grpc_python_plugin/1.32.0/macos/x86_64/grpc_python_plugin",
+        "1.32.0|linux_arm64 |9365e728c603d64735963074340994245d324712344f63557ef3630864dd9f52|5233664|https://binaries.pantsbuild.org/bin/grpc_python_plugin/1.32.0/linux/arm64/grpc_python_plugin",
+        "1.32.0|linux_x86_64|1af99df9bf733c17a75cbe379f3f9d9ff1627d8a8035ea057c3c78575afe1687|4965728|https://binaries.pantsbuild.org/bin/grpc_python_plugin/1.32.0/linux/x86_64/grpc_python_plugin",
     ]
-    default_url_template = (
-        "https://binaries.pantsbuild.org/bin/grpc_python_plugin/{version}/"
-        "{platform}/grpc_python_plugin"
-    )
-    default_url_platform_mapping = {
-        "macos_arm64": "macos/x86_64",  # TODO: Build for arm64.
-        "macos_x86_64": "macos/x86_64",
-        "linux_arm64": "linux/arm64",
-        "linux_x86_64": "linux/x86_64",
-    }
+
+    def generate_url(self, plat: Platform) -> str:
+        prebuilt_version, grpc_version = self.version.split("+")
+        plat_str = {
+            "macos_arm64": "macos-universal",
+            "macos_x86_64": "macos-universal",
+            "linux_arm64": "linux-aarch64",
+            "linux_x86_64": "linux-x86_64",
+        }[plat.value]
+
+        return f"https://github.com/nhurden/protoc-gen-grpc-python-prebuilt/releases/download/{prebuilt_version}/protoc-gen-grpc-python-{plat_str}-{grpc_version}"

src/python/pants/backend/codegen/protobuf/python/rules_integration_test.py

@@ -408,6 +408,7 @@ def test_grpclib_plugin(rule_runner: RuleRunner) -> None:
     )
 
 
+@pytest.mark.platform_specific_behavior
 def test_all_plugins(rule_runner: RuleRunner) -> None:
     rule_runner.write_files(
         {